1. The Field of the Disclosure
The present disclosure relates generally to the shape of wind tower structural members.
2. Background Information
As illustrated in FIG. 1, in the wind power industry, a space frame wind tower 10 may include a plurality of tower legs, known as space frame tower legs 13. Space frame tower legs are currently made using existing structural shapes. For instance, existing structural tower legs may be made from angle iron, H-beams, pipe, and other structure comprising cross sectional shapes that are readily available. The two most common shapes used as tower legs are the angle iron and the pipe.
Referring to FIGS. 2 and 3, it will be appreciated that using a pipe 20 for the tower leg 13 allows for a single structural member, namely the pipe 20, to be used. Using a single structural member removes the complexity of having to assemble a structural leg having a shape sufficient to withstand and bear the loads that will be encountered in the wind tower.
It will be appreciated that the pipe 20 does not have sufficient structure that can be used as additional connection points, which are needed up and down the length of the leg. Typically, to create these additional connection points (an example would be for joining the bracing to the leg member) on a leg made from pipe, members or gusset plates 22 are welded at 26 to the side of the pipe 20. Welding, while not largely problematic in other industries, is a serious weak point in a tower used for supporting a wind turbine, and to overcome the induced fatigue weakness due to the weld, the wall thickness of the structural member is increased, which increases the cost of the design.
Referring now to FIGS. 4 and 5, it will be appreciated that using the angle iron design for a tower leg 13, a leg 13 can be created where welding is not required. However, in such a design a single angle iron 40 is not sufficient or ideal for a tower leg, so a “built” structural shape is needed or created for the leg 13 by bolting multiple angle irons 40 together to create a new shape as illustrated in FIG. 4. Such a design adds cost and complexity to the structure, but also avoids the need for welds, which can create a weak point in a wind tower.
With wind power demand increasing across the world, there is a need to develop a tower structure for wind turbines that is more cost efficient and that also reduces the amount of raw materials required. The present disclosure will describe structures providing such advantages as well as other advantages.